It is well known that liquid fuel contains components that can degrade during engine operation and form deposits. Such deposits can lead to incomplete combustion of the fuel resulting in higher emissions and poorer fuel economy. Detergents are well known additives in liquid fuels to help minimize deposit formation. As the dynamics and mechanics of an engine continually advance, the requirements of the fuels and additives must evolve to keep up with these engine advancements. For example, today's engines have injector systems that have smaller tolerances and operate at higher pressure to enhance fuel spray to the compression or combustion chamber. Deposit prevention and reduction has become critical to optimal operation, and therefore there is a need for detergents capable of providing acceptable performance in a liquid fuel to promote optimal engine operation.
Furthermore, there is a dramatic difference between indirect fuel injected diesel engines, and more modern high pressure common rail (HPCR), direct fuel injected diesel engines. Also, low sulfur diesel fuels and ultra low sulfur diesel fuels are now common in the marketplace for such engines. A “low sulfur” diesel fuel means a fuel having a sulfur content of 500 ppm by weight or less based on a total weight of the fuel. An “ultra low sulfur” diesel fuel (ULSD) means a fuel having a sulfur content of 15 ppm by weight or less based on a total weight of the fuel. Fuel injectors in an HPCR engine perform at much higher pressures and temperatures compared to older style engines and fuel injection systems. The combination of low sulfur or ULSD and HPCR engines have resulted in a change to the type of injector deposits and frequency of formation of injector deposits now being found in the marketplace.
Hence, fuel compositions for direct fuel injected engines often produce undesirable deposits in the internal engine surfaces and fuel filters. Accordingly, improved compositions that can prevent deposit build up, maintaining “as new” cleanliness for the vehicle life are desired. Ideally, the same composition that can clean up dirty fuel injectors restoring performance to the previous “as new” condition would be equally desirable and valuable in the attempt to reduce air borne exhaust emissions and to improve the power performance of the engines.
It is known to use certain polyisobutenyl succinimide (PIBSI)-derived quaternary ammonium salt detergents as additives in fuel compositions to promote optimal engine operation, for example, increased fuel economy, better vehicle drivability, reduced emissions and less engine maintenance by reducing, minimizing and controlling deposit formation. Such quaternized detergents are typically derived from traditional PIBSI fuel additive compounds that have pendant tertiary amine sites which can be alkylated, i.e. quaternized, by a quaternizing agent, such as propylene oxide. Examples of such reactions and reaction products are included in U.S. Pat. No. 8,147,569.
A new improved class of quaternary ammonium salt detergents derived from polyisobutenyl succinamides and/or esters have also been disclosed. Such additives are claimed to be more thermally stable than the PIBSI-derived quaternary ammonium salt detergents and may be manufactured by a less energy-intensive process. Examples of such reactions and reaction products are included in U.S. Publication No. 2012/0138004.
Quaternary ammonium salt detergents often require the use of flammable and dangerous epoxides such as propylene oxide and further require the use of specialized and expensive pressure vessels for their production. The alkoxylation step requires a carboxylic acid as proton donor. The resulting carboxylate may lead to deposit formation and other issues related to carboxylate salts being present in the additive and fuel.
In addition, the polyisobutenyl succinamide and/or ester intermediates tend to be very viscous and difficult to handle during the manufacturing process. The reaction products often contain varying amounts of polyisobutenyl succinimides rendering it difficult to charge a correct amount of epoxide and or acid to the reaction mixture.
Lastly, conventional quaternized PIB/amine ammonium salts tend to negatively impact the demulsibility of fuels such as diesel fuels.
The present invention relates to a new class of alkoxylated quaternary ammonium detergents which offer significant improvements over the prior art polyisobutylene succinimide, amide and or ester derived PIB/amine quaternary ammonium salts. The process requires no specialized and/or expensive pressure reactors. The resulting quaternary salts not only afford improved detergency performance but also provide improved demulsibility.
In accordance with the disclosure, exemplary embodiments provide a fuel additive and its preparation for a engine, a fuel containing the additive, a fuel additive concentrate, a method for improving performance of fuel injectors and a method for cleaning fuel injectors for an engine. The fuel additive includes a quaternary ammonium salt derived from a reaction of a hydrocarbyl substituted anhydride, a tertiary amine and a hydroxyl-containing epoxide, wherein the tertiary amine is devoid of primary and secondary amino groups. The fuel additive concentrate comprises the fuel additive and one or more components and/or solvents.
Another embodiment of the disclosure provides a method of improving the injector performance of a direct fuel injected engine. The method includes operating the engine on a fuel composition containing a major amount of fuel and from about 5 to about 200 ppm by weight based on a total weight of the fuel composition of a quaternary ammonium salt derived from a reaction of a hydrocarbyl substituted anhydride, a tertiary amine and a hydroxyl-containing epoxide, wherein the tertiary amine is devoid of primary and secondary amino groups.
A further embodiment of the disclosure provides a method of operating a direct fuel injected diesel engine. The method includes combusting in the engine a fuel composition containing a major amount of fuel and from about 5 to about 200 ppm by weight based on a total weight of the fuel composition of a quaternary ammonium salt from a reaction of a hydrocarbyl substituted anhydride, a tertiary amine and a hydroxyl-containing epoxide, wherein the tertiary amine is devoid of primary and secondary amino groups.
An additional embodiment of the disclosure provides a method for making a quaternary ammonium salt for use as a fuel detergent. The method includes combining, as reactants, a hydrocarbyl substituted anhydride, a tertiary amine and a hydroxyl-containing epoxide, and reacting the reactants under conditions sufficient to form a quaternary ammonium salt. The tertiary amine is devoid of primary and secondary amino groups.
An advantage of the fuel additive described herein is that the additive may not only reduce the amount of deposits forming on fuel injectors and be effective to clean up dirty fuel injectors sufficient to provide improved power recovery to the engine, but the additive may also unexpectedly enhance the demulsibility of the fuel composition.
Additional embodiments and advantages of the disclosure will be set forth in part in the detailed description which follows, and/or can be learned by practice of the disclosure. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.